Protective device



March 27, 1928.

E. E. F. CREIGHTON PROTECTIVE DEVICE Filed Sept. 5. 1924 Inventor;

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2? HisAttorney.

w s; Mar'. 2 7,1928.

UNITED STATES PATENT OFFICE.

ELIEB E. I. OBBIGETON, OI SCKENBC'I'ADY, NEW YORK, ASSIGNOB TO GENERAL ELIO- TBIC COIPANY, A CORPORATION OI' N EW YOBK.

rnomc'rxva nnvrcn.

Application filed September 5,1924. Serial No. 736,186.

My invention relates to protective devices for" electrical apparatus including line conductors whereby abnormal potential charges, such as atmospheric disturbances, static .6 accumulations, resonance of frequencies, switchin surges, etc., may be carrled ofl' without injury to the apparatus.

The object of my invention is to provide an improved protective device or arrester which is simple and inexpensive to construct and has improved operatingcharacteristics.

. The improved arrester hereinafter .d-isclosed and involving my invention is of the .so-called multigap type and is well adapted for usew in the e ectrlcal systems operating :at pot'entials of a few thousand volts.

he multigap arrester is well-known in the art. In its most common form is com prises a plurality of conducting members usuall in the form of brass cylinders with a smallair space of insulation between adjacent cylinders, to form a series of short air ga The aggregate length of these air gaps or any given pptential is considerably greater than could employed if a single gap were used.' In the multigap arrester, the electrostatic capacity of the cylinders or other conductors is relied on, in a measure,

to assist in starting a spark across the gaps and thereby initiate a flow of lightning current when an abnormal potentlal arises on the line. When this ionization occurs there. seems to be a progressive spark beginning on the "line side of the series of gaps and traveling along the successive gaps to the other terminal. The time interval of this progression of the discharge is, of course, extremely small, estimated in billionths ofia second from cylinder to cylinder, but the total time interval. oi the arrester is, nevertheless, ap-

preciable in considering the protection of insulation. For practical purposes, as distinguished from purely scientific investigations, it is not customary to express the time of establishment of sparks across the circuit of a lightning arrwter but an easier and simplerexpression is used. In other words, the

quickness of discharge is measured in the laboratory by the length of an equivalent sphere gap in parallel with the arrester or insulation upon which an-abnormally high voltage is impressed. The gap or circuit which first begins to discharge relieves the other parallel circuit of high voltage. Consequently, the fastest gap is the only one that more clearly show the construction;- Fig. 2

ing the circuit arrangement; Fi 5 is a visibly sparks. With this method available for measuring the equivalent sphere ap, it is possible for any one familiar with t is art to determine whether one lightning arrester discharges more quickly and better. than another.

In m Patent No. 1,071,710, September 2,. 1913, I ave used auxiliary electrodes, which I called antennae, to cause the circuit of a multigap arrester to be established more Ill quick y than'could be done without the, use. of antennae. Y

My present invention is somewhat along I the same lines but is simpler in that no auxiliary electrodes are used, and is much cheaper to apply to a multigap lightning arrester. As a'matter of fact, there are no auxiliar parts used to act inductively on. th multiga fly invention will be better understood (6 from the following description taken in con-- nection with the accompanying drawing, and its scope will be pointed out in the ap ended claims.

11 the drawing, Fig. 1 is an elevation of anarrester constructed accordin to my invention with the cover remove .and with parts of the enclosing tube brokenaway to is a top view of the same with the cover. removed; Fig. 3 is an elevationon a larger scale of one of the three insulating strips carryin' the electrodes; Fig. 4 is a development 0 the current carrymg members showdetail [of one of the plates or .e ectrodes' I Fig.- 6 is an elevation on a smaller scale 0 the complete arrester with parts broken away to more clearly show the construction; and Fig. 7 is a top view of a modified form. In my present lnvention I divide the total length of circuit comprised of the multigaps into several parts, three in the illustration, andplace these three arts side by side in an insulatin tube we as porcelain, lass or quartz. nFigs. 1 and 2 such a tufie is shown at 1, having the general form' of an equilateral triangle with longitudinal partitions 2 connectin the side's-and formi three longitudinal c ambers 3. :Within eac 106 chamber is a supporting block or-strip 4 which may be of porcelain or other. suitable, material to which thin discharge lates 5*? are secured, as for example, by lts 6. For convenience in the description'the strips 110 are designated A, B, and C. The plates 5, as illustrated on a larger scale in Fig. 5, are angular in form and each has a face 7 formed with a series of small projections and other faces 8 and 9 engaging the strip 1. The plates are arranged in staggered relation as shown by Figs. 1 and 4 with the faces bearing the projections facing each other. Each of the extreme end plates of each strip 4 has an extension 10 which projects through a slot in the end of the strip 4 for the purpose of making electrical connection therewith. A spring connector 11 is secured to the extensions 10 at the lower ends of each of strips A and B and the upper ends of these connectors engage each other through a suitable openin v12 formed in the intervening partition 2 of tube 1. The-extensions at the upper ends of strips B and C are connected to other by a connector 13 attached to the tu e 1. To the upper extension 10 of strip A is attached a terminal connector 14 which projects through a suitable opening in the tube 1, and the lower extension 10 of strip C is shown connected to a metal tube 15 which is adapted to connect that extension with earth and which also supports strip C in the tube. Strip B is supported on an insulating rod 16 which may be of wood, and strip A is supported by a resistance rod 17 whose upper end is in electrical connection with the lower extension 10 of strip A and whose lower end is in contact with the metal plate 18. The plate 18 has three tongues 19 which are adapted to slip into grooves 20 formed in the walls of the tube 1. A groundconnection is made -to the bottom plate 18 by attaching the ground wire 21 thereto. In making this ground connection, I prefer to attach the ground wire to the plate 18 by solder having a relatively low melting point and at a polnt opposite the resistance rod 17 for, by this arrangement, I obtain the advantage that should the arrester become short-circuited as a result of a direct stroke or other abnormal condition of discharge, the heating of the resistance rod by the power currentwill melt the solder and allow the ground wire to drop. A visual indica-- t-ion of the particular arrester at fault is thus. given to an observer on the ground. Power transmission maybe at once resumed by simply closing the circuit breaker after such a fault has occurred. The arrester may be restored to normalv operating condition at any convenient time. A cap 23 covers the top of the arrester tube 1.

By the above described construction it will be seen that the total length of the normal discharge circuit is divided into several columns, three in particular form illustrated, the three columns being arranged parallel to each other and occupying separate chambers in the insulating tube 1. Current entering by the terminal l l'follows down the first column A, jumps the gaps between the plates 5 in a zigzag manner where it meets the resistance rod 17 From there it follows up column B and down column O in the. same manner, finally escaping to ground through the pipe 15, plate 18 and ground lead 21. When a lightning or other abnormal discharge comes in at the top of column A, it must start sparks across the gaps of this column and some of the 'charge may pass through the resistance 17 to ground.

The abnormal voltage of this first column of electrodes induces simultaneously a charge on both of the other two columns of electrodes, starting sparks across their gaps. Thus the complete circuit from the upper electrode 14, column A, to 'the lower electrode of column 0 through the three columns, requires very little morevoltage than is necessary to spark over the first column.

I am aware that resistances have been used before to shunt part of the gaps of an arrester between the line and ground and that arr-esters have been constructed having mul tigaps in a more or less open zigzag form, but as far as I am aware a multigap arrester having a zigzag relation between the.

parts has never before been constructed where the parts are in such close proximity as to give valuable reductions inthe equivalent sphere gap or, in common parlance, rapid discharge. The effect is obtained by using comparatively thin walls between the columns A, B, and G, as shown for example by Figs. 1 and 2 composed of insulating material such as porcelain, glass, fusedquartz or other equivalent material. The use of fused quartz has the additional ad vantage of permitting the ultra-violet light from its sparks in one column to play upon the gaps of the other columns. Ultra-violet light, as is well known, ionizes a gap and permits a lower voltage to start a spark than would be necessary without the ultraviolet light. When fused quartz is used to enclose the columns of electrodes and space them from each other, it may be found more expedient to enclose each column in a separate quartz tube 23 as shown in Fig. 7 and enclose the three tubes in a; round or a triangular case 24 which may be of insulating material such as porcelain, for example, or may even be metallic.

Rapid discharge of, the arrester due to the electrostatic effect of the columns of electrodes upon each other is increased by reason of the relativel large electrostatic capacity between the co umns.. This resultsparticularly from those portions 8 and 9 of the plates 5, Fig. 5, which are'secured against the strip 4 and by which capacitance is ill - accent the other two colunms. It will be noted,

by reference to Fig.v 4 that a circuit is comp etc from the line terminal 14 through the gaps of the. first column and resistance 17,

which ma be made comparatively low, to ground. he suddenness of the establishment of current is verygreat-in mathematical language is great. In consequence of these conditions an factors a considerable electromagnetic induction between columns is obtainable.

I havexused for illustration but three columns for this arrester, but it. is evident through the plate awa that as many as five, seven, nine, etc. may be used according to convenience and total voltage ".of the circuit for which its arrester is designed.

One of the difiiculties met in the use of multigap arresters is the tendency of the discharge to melt down more metal in the crater of the arcs than is needed to supply the conducting metallic vapor. This molten metal has a tendency to globulate and in so doing close the gap wit-h molten metal. A-metallic connection across the gaps destroys any possibility of the current being interrupted by the extinguishment of the arc in the gap and the reestablishment of the air insulation through the series of gaps after the 'abnormal discharge has taken place. The heavy currents are derived not only from the abnormal charges on the line, but also from the regularly nerated power.

In order to overcome-this tendency of electrodes to short circuit by an over-supply of molten metal, I use metal so thin that heavy discharges will push themolten metal from the gap. Plates too thin will be a ected by the many usual discharges that take place, and artially damage it. Plates too rthick wil not be meltedall the way through by the dangerous unusual discharges and will be inefiective. The thickness of plate which is most advantageous will, therefore depend upon the particular service for which the arrester as much as several times the cost ofthe arrester itself, there is a distinct advantage to be gained from the point of view of the user if, in the'event that the arrester becomes disabled, the affected parts can be readily replaced without disturbing the mounting of" the arrester. Such a renewal is possible with the arresterherein described for'should the groups of electrodes become worn in the course of time by lightning discharges therethrough, it is a very' sim le matter to remove the holders 4 from the ttom of the tube 1 by removing the plate 18 or the-cap substitute others, thus reloadin thearrester without in any way a ecting the mounting. I

' What I claim as new and desire to secure by Letters Patent of the United States, is,-

1. A multigap arrester comprising a plurality of adjacent columns of electrodes spaced to form spark gaps between the electrodes, said arrester comprising an enclosed compartment for each column, said compartments comprising walls transparent to ultra violet rays whereby the gaps in one of said columns may be ionized when a dischar takes place along another one of sa d columns.

2. A multigap arrester comprising a plurality of columns of spaced electrodes and means connecting said columns in series, said columns being arranged in and adjacent each other whereby the electromagnetic induction from a discharge in one column causes ionization in another column.

23 and parallel relation.

3. A, multigap arrester having electrodes spaced to form aps between each other, the gaps and the e ectrodes being arran in serial order, one section of the series of electrodes overlapping another section of the same series, the overlappin being such that comparat ve y distant gaps of the series are located nearer each other than intervening gaps in the series whereby sparking in one section between the electrodes causes sparking to be started across gaps in the overlapping section.

4. A multigap arrester havin electrodes spaced toform ps between eac other, the gaps and the e ectrodes being arranged in serial order one section of the series ofelectrodes overlapping another section of the same series, the overlappin arrangement being such that comparative y distant gaps of the series are located nearer each other than intervening gaps in the series, said electrodes being each provided with extended metallic portions remote from the sparking faces of the electrodes, the saidextended portions of one section of the seriesbeing in inductive relation with r t to the extended por tions of the other section of the series.

5. A multigap arrester havingl electrodes spaced to form gaps between eac other, the gaps and the e serial order, one. section of the seriesof electrodes overlapping another section of the same series, the overlapping arrangement being such that comparatively distant gaps of the series are located nearer each other than intervening gaps in the series whereby sparking m one section between the elecectrodes being arranged in trodes causessparking to be started across gaps in the overlapping section, each section being enclosed in a transparent quartz tube.

6. A multigap arrester'having electrodes 5 spaced to form gaps between each other, the

7. A multigap arrester having electrodes spaced to form gaps between each other, the the gaps and the electrodes being arranged in serial order, one section of the series of electrodes overlapping another section of the same series, the overlapping arrangement being such that comparatively distant gaps of the series are located nearer each other than intervening gaps in the series whereby sparking in one section between the electrodes causes sparking to be started across gaps in the overlapping section, each section being enclosed in a transparent quartz tube, one of said sections be ng shunted by an impedance element.

In witness whereof, I have hereunto set my hand this 4th day of September, 1924;.

ELMER E. F. GREIGHTON.

CERTIFICATE or CORRECTION.

a No. 664, 194.

Granted March 27 1928, to

ELMER E. F. cREIGHToNI It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page I, line 18, tor

word "is" read "it", and line 74, for the word "gap" read "gaps"; page 4, line 21, claim 7, strike out the article "the"; and that thesaid Letters Patent should be read with these corrections therein that the same ma conform to the record of the case in the Patent Office. 1 .Signed arid sealed this 1st day of May, A. l). 1928;

M. .l. Moore,

. Acting Commissioner 0f Patents.

the

GERTEFIG ATE m? CGRREGTION.

Patent No. i,664,1%. Granted Mareh 27, 1928, to

ELMER E. F. CREIGHTON.

he primed specifieeiiem 0f the tent requiring cerreetism ioilews: Page i, Zine 18, for the word "is" rem "it", and Hm: 74, fur the Ward "gap" read "gaps"; page 4, line 21, chain: 7, strike out the article "the; that ike said Letters Eaient shouid be read WW1 these em'reeiiees therein that the same een'ierm tn the reeerd sf"; the ease in the Patent Qiiiee.

Signed mad seaied this Let day 0% May, A. D. 1923.

It is hereby certified that errer aepee re in t above numbered pa (Seal) 

